Toroidal transformer connections

[Dale gribble]

Hi, I'm just up grading my power supply but keep blowing fuse's, can somebody check I have my cables connected correctly.

I 've upload a PDF of the transformer specs.

I have mains positive connected to Brown and neutral connected to Blue on the primary side (UK).

On the secondary I have red and yellow connected together and black and orange connected together.

This model is the 2 x 50 @ 10amps. I currently only have a 4a fuse on the primary side which keeps on blowing. Thats all i have knocking around my garage i do plan to order some 10amps fuse. I thought with no load on the power supply I could get away with the 4 amp fuse for trials.

Do these transformers have a large surge current on start up or are my connections incorrect?

[davidmb]

Hi Dale,

Toroidal transformers are notorious for high inrush current at switch on, best bet would be a time delay fuse, most domestic mains fuses are fast fuses, also
how have you mounted your transformer, the bolt that comes with the clamping plates must NOT form a complete electrical circuit around the toroid.

From your description your secondaries windings are connected correctly.

[Al_The_Man]

If the fuse you are using is a fast blow, at 4a it may not be high enough for both transformer inrush and the capacitor charge, if these are also connected.
Try it without the secondaries connected to see if it hangs in with just the transformer.
Al.

[Dale gribble]

Hi, thanks 4 the replys. I did not use the bolt on the transformer as i am just testing at the minute. 1st test i did have the bridge rectifier connected. 2nd test i connected just the transformer, fuse blew on both tests. I've now ordered some 10 amp slow blow fuses. Thanks 4 everyones input. P.s text input via mobile phone